# ---
# title: 532. K-diff Pairs in an Array
# id: problem532
# author: Indigo
# date: 2021-06-22
# difficulty: Medium
# categories: Array, Two Pointers
# link: <https://leetcode.com/problems/k-diff-pairs-in-an-array/description/>
# hidden: true
# ---
# 
# Given an array of integers `nums` and an integer `k`, return _the number of
# **unique** k-diff pairs in the array_.
# 
# A **k-diff** pair is an integer pair `(nums[i], nums[j])`, where the following
# are true:
# 
#   * `0 <= i, j < nums.length`
#   * `i != j`
#   * `|nums[i] - nums[j]| == k`
# 
# **Notice**  that `|val|` denotes the absolute value of `val`.
# 
# 
# 
# **Example 1:**
# 
#     
#     
#     Input: nums = [3,1,4,1,5], k = 2
#     Output: 2
#     Explanation: There are two 2-diff pairs in the array, (1, 3) and (3, 5).
#     Although we have two 1s in the input, we should only return the number of **unique** pairs.
#     
# 
# **Example 2:**
# 
#     
#     
#     Input: nums = [1,2,3,4,5], k = 1
#     Output: 4
#     Explanation: There are four 1-diff pairs in the array, (1, 2), (2, 3), (3, 4) and (4, 5).
#     
# 
# **Example 3:**
# 
#     
#     
#     Input: nums = [1,3,1,5,4], k = 0
#     Output: 1
#     Explanation: There is one 0-diff pair in the array, (1, 1).
#     
# 
# **Example 4:**
# 
#     
#     
#     Input: nums = [1,2,4,4,3,3,0,9,2,3], k = 3
#     Output: 2
#     
# 
# **Example 5:**
# 
#     
#     
#     Input: nums = [-1,-2,-3], k = 1
#     Output: 2
#     
# 
# 
# 
# **Constraints:**
# 
#   * `1 <= nums.length <= 104`
#   * `-107 <= nums[i] <= 107`
#   * `0 <= k <= 107`
# 
# 
## @lc code=start
using LeetCode

function find_kpairs(nums::Vector{Int}, k::Int)
    cntr = counter(nums)
    res = 0
    if k > 0
        for (ky, vl) in cntr
            res += (ky - k in keys(cntr)) ? 1 : 0
        end
    else
        for (ky, vl) in cntr
            res += ifelse(vl > 1, 1, 0)
        end
    end
    return res
end
## @lc code=end
